2. 外语
  3. In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers.

In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers.

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问题 In addition to conventional galaxies, the universe contains very dim galaxies that until recently went unnoticed by astronomers. Possibly as numerous as conventional galaxies, these galaxies have the same general shape and even the same approximate number of stars as a common type of conventional galaxy, the spiral, but tend to be much larger. Because these galaxies’ mass is spread out over larger areas, they have far fewer stars per unit volume than do conventional galaxies. Apparently these low-surface-brightness galaxies, as they are called, take much longer than conventional galaxies to condense their primordial gas and convert it to stars—that is, they evolve much more slowly.
These galaxies may constitute an answer to the long-standing puzzle of the missing baryonic mass in the universe. Baryons—subatomic particles that are generally protons or neutrons—are the source of stellar, and therefore galactic, luminosity, and so their numbers can be estimated based on how luminous galaxies are. However, the amount of helium in the universe, as measured by spectroscopy, suggests that there are far more baryons in the universe than estimates based on galactic luminosity indicate. Astronomers have long speculated that the missing baryonic mass might eventually be discovered in intergalactic space or as some large population of galaxies that are difficult to detect.
The author of the passage would be most likely to disagree with which of the following statements?
选项 A、Low-surface-brightness galaxies are more difficult to detect than are conventional galaxes.
B、Low-surface-brightness galaxies are often spral in shape.
C、Astronomers have advanced plausible ideas about where missing baryonic mass might be found.
D、Astronomers have devised a useful way of estimating the total baryonic mass in the universe.
E、Astronomers have discovered a substantial amount of baryonic mass in intergalactic space.
答案E
解析 Inference
This question involves identifying which answer option potentially conflicts with the information the author has provided in the passage. The second paragraph indicates that astronomers’ estimates of the baryonic mass of the universe is lower when measured using luminosity than it is when measured using spectroscopy (lines 21-25). The final sentence states that astronomers have speculated that the missing baryonic mass might be discovered in intergalactic space or in hard-to-detect galaxies (lines 25-29). Although the passage does indicate that the discovery of dim, low-surface-brightness galaxies might help account for the missing baryonic mass (lines 15-17), the passage provides no support for the possibility that baryonic mass has been discovered in intergalactic space.
A The passage indicates that low-surface-brightness galaxies went unnoticed until recently, unlike conventional galaxies.
B The passage indicates that low-surface-brightness galaxies have the same general shape as spiral galaxies.
C The passage describes two possible explanations astronomers have given for the missing baryonic mass, one of which was made more plausible by the discovery of low-surface-brightness galaxies.
D The passage indicates that astronomers have used spectroscopy to estimate baryonic mass and gives no reason to suspect that this method is not useful.
E Correct. The passage does not indicate that astronomers have found any baryonic mass in intergalactic space.
The correct answer is E.
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